Assessing different oil sources efficacy in reducing environmental heat-stress effects via improving performance, digestive enzymes, antioxidant status, and meat quality

Adding oil to the feed of genetically improved broilers is necessary to provide energy requirements, in addition to enhancing metabolism, growth performance, immune response. This study aims to reveal the effect of adding different oil sources in the diets of broilers exposed to environmental heat stress on performance, digestibility, oxidative status, plasma lipids, fatty acids content, and meat quality. Six hundred twenty-five one-day-old broiler chicks were randomly distributed to five groups as follows: the first group fed a diet without oil (CON) as a control, while the second to the fifth group fed a diet containing soy oil (SO), corn oil (CO), olive oil (OO), and fish oil (FO), respectively. Results indicated a significant deterioration in growth performance, carcass traits, and oxidative state with a significant decrease in carcass quality in heat-stressed chickens fed the CON diet. Results showed increased growth, enhanced feed conversion ratio, and carcass dressing in broilers fed the oil-supplemented diet compared to the control diet, however, the digestive enzymes activity was not affected by receiving an oil-supplemented diet. The best performance was in chickens fed OO and SO, compared with FO and CO. Plasma aspartate aminotransferase (AST), and alanine aminotransferase (ALT) increased in broilers fed an oil-supplemented diet. Plasma high-density lipoprotein (HDL), and superoxide dismutase (SOD) remarkably increased in broilers fed OO, whereas the malondialdehyde (MDA) decreased compared to the other groups. Adding different dietary oil sources enhanced the breast muscle's fatty acid composition. Broiler diets supplemented with oils positively affected meat quality by enhancing color measurements, and TBA values, while the best were in chicken fed OO. It was concluded that adding dietary oil at 3% in the diets of broiler chicken exposed to environmental heat stress positively affected growth performance, enhanced oxidative status, and meat quality, best results were in broilers fed a diet that included olive oil.

Understanding the environmental conditions surrounding the bird and how to control it are some of the poultry industry success factors.One of the various environmental stress factors is heat stress, which has a detrimental effect on the health of the bird and its productivity 1 .Thermal stress results from the relationship between the amount of energy produced by the bird and the amount of energy emitted from the bird's body to the surrounding environment, which causes a defect in the bird's body.Modern broiler breeds have a high metabolic activity that produces a high amount of heat from the body, which makes them more sensitive to heat stress 2 .The broilers exposure to high temperature leads to behavioral, immune, and physiological changes in an attempt to resist heat stress, which results in significant economic losses in the poultry industry.Experts began to work on solving the problem of heat stress in the poultry industry by developing houses (including building construction, pad cooling systems, and ventilation), however, this development did not give the desired results, as well as the high costs of this technology hindered its use in developing countries.The initial symptom of heat stress

Plasma parameter
All the added oil sources increased plasma HDL values, whereas there were variations in ALT and AST levels according to the added oil, as shown in Table 3. ALT and AST levels significantly decreased in broilers fed the OO and CO (p < 0.05) compared to FO, SO, and CON groups.However, the ALT and AST levels were similar in chickens that received CON and SO (p < 0.05), while FO was the highest.The plasma content of thyroid hormones, including T3 (triiodothyronine) and T4 (thyroxine) was significantly higher in chicks fed on an oil diet compared to the control group (p < 0.05).Compared to the control group, the group that was fed CO had Table 1.Effect of adding different dietary oil sources on growth performance of broilers under environmental heat stress a-c Means within the same row with different superscripts differ.CON without additional oil, SO soy oil, CO corn oil, OO olive oil, FO fish oil, SEM standard error of means.BWG body weight gain, FI feed intake, FCR feed conversion ratio (g/g), EPEF European Production Efficiency Factor.

Digestive and antioxidative enzymes activity
Data in Table 4 displays the impact of oil addition on the activities of digestive enzymes and antioxidative enzymes.Supplemented oils enhanced the oxidation status of broilers exposed to environmental heat stress, where the SOD level increased and the MDA level decreased (p < 0.05) while the GPx level was not affected.MDA levels decreased in the chickens fed OO and SO compared to chickens fed CO, and FO.SOD levels increased in chickens fed OO, FO, and SO compared to chickens fed CO, and CON.Furthermore, the digestive enzymes activities (like amylase, trypsin, and lipase) of broilers had no significant differences among the experimental groups (p < 0.05).However, there was an insignificant numerical increase in amylase level with the inclusion of OO and CO (p = 0.061).In addition, the inclusion of OO, CO, and SO led to an insignificant numerical increase in lipase (p = 0.058).

Fatty acid profiles of breast meat
Data on the fatty acid profile of broiler chicken meat fed different types of oils under heat stress conditions are shown in Table 5.The saturated fatty acids content (SFA) of broiler meat, especially the palmitic acid (C16:0) was not significantly affected by the oil supplements in broiler diets.However, myristic acid (C14:0) increased in the meat of the CON group, while it decreased in the SO group.Oleic acid (C18:1 ω9) content was higher in groups fed on OO and FO compared to other groups.Furthermore, linoleic acid (C18:2 ω6) content was higher in the group fed on SO compared to other groups.Broilers fed FO and OO had significantly higher C22:6 ω3 and C18:1 ω9, respectively, compared with those fed SO and CO.Broilers fed on SO had the highest linolenic acid (C18:3 ω3) while the lowest value was found in the CON group.Compared to the control group, the chickens fed SO and OO showed a significant increase in USFA.Data PUFA: SFA ratio indicated that broilers fed on FO exhibited a lower ratio of PUFA: SFA while broilers fed on SO had a higher ratio than other oil-feeding groups.
Data of ω6:ω3 ratio revealed that the meat of broiler fed on fish oil (FO) had the lowest ratio, followed by broiler fed on olive oil (OO) compared to other groups.www.nature.com/scientificreports/

Physicochemical characteristics of meat
Table 6 shows the physicochemical characteristics of broiler chicken meat fed different types of oils under heat stress conditions.No significant differences were found in pH values for cooking loss and chilling loss of broiler meat.Data of shear force values showed that the meat of CON, FO, and OO feeding groups had lower shear force values (more tender) than the other groups.Color measurements of broiler meat showed significant differences in L* values.The meat of the broiler fed on olive oil (OO) had a higher L* value followed by the meat of the control group (CON), while no significant differences were found between the meat of the SO and CO groups.However, the meat of FO had the lowest value.Furthermore, data showed that the meat of the FO and SO feeding groups had the highest a* value, and no significant differences were found between the other groups.Data of b* value showed that meat of FO, OO, and CON groups had the highest b* and the differences were insignificant.Moreover, no significant differences were found between the SO and CO groups which had the lowest b* value.Data on the TBA value of broiler chicken meat fed different types of oils under heat stress conditions are shown in Table 8.The meat of broilers fed on the FO and OO had the lowest TBA value, while, the highest TBA value was found in the meat of the CON group.

Discussion
Heat stress is one of the most important problems that the poultry industry suffers from due to its detrimental effect on performance and meat quality, leading to great economic losses.Usually, oils and fats are used in poultry feed on a large scale to provide the bird's energy needs.In addition, many previous studies indicated that adding oils or fats during high environmental temperature reduces harmful effects by improving chicks' growth and enhancing antioxidant status and welfare 1, 21 .
Nutritionists have used many nutritional modifications or additions in an attempt to mitigate the harmful effects of any stress on the bird.Therefore, this study aimed to add different sources of oils to reduce the negative effects of heat stress on the bird.In the current experiment, broilers showed signs of heat stress, such as panting and straightening the wings.The results of the current study indicated a significant deterioration in the growth performance of chickens fed a diet without oil, while there was an improvement in the BWG and FCR of broiler chickens fed diets supplemented with oil under environmental heat stress.Chickens fed on OO and SO had better growth performance than the other groups, while the best performance was in broilers fed olive oil (OO).This is consistent with the results of previous studies, which stated that adding oil enhanced the growth performance of chickens exposed to high temperatures 21,22 .The improvement in growth performance can be explained by the fact that the addition of oil led to the palatability of diets, the oil enhances the absorption of fat-soluble vitamins, reduces the dustiness of feeds, and decreases the rate of food passage within the digestive system 23,24 , thus improving the utilization of nutrients, as well as, an appositive impact on humoral immunity, which is reflected in growth performance.In addition, enhanced growth of broilers fed on oil could be due to higher UFA and medium-chain fatty acids (MCFA), MCFA is burned exclusively and rapidly for energy production 25 .In this study, there was a difference in the rate of improvement in BWG and FCR between the different types of oil added, where olive oil had the best BWG and FCR.The improved performance in chickens fed olive oil is either due to its high content of monounsaturated fatty acids (MUSF) compared to saturated fatty acids (SFA) or to the balance between the ratio of omega 3 and omega 6 (1:7), that ratio is essential because elevated ω-6 reduces the benefits of ω-3.Furthermore, it contains a large proportion of omega-9, which makes it one of the best and healthiest oils.Olive oil also contains some biologically active compounds that have a role in reducing the oxidative stress harmful effects during the stress period, which is reflected in the enhancement of broiler health and performance.Our results confirm that chickens fed an oil-included diet had better tolerance to environmental heat stress than chickens fed a ration without oil.The group fed on olive oil had the most tolerance to environmental heat stress than other groups.The reason for the variance in growth performance can be explained by the content of each oil of saturated and unsaturated fatty acids.Similar results were obtained by Nobakht et al. 24 and Khatun et al. 26 .Moreover, the FI was not affected by the inclusion of the dietary oils, this result was in agreement with Khatun et al. 26 .In contrast, some studies showed that FI was affected by the type of oil added to the diet by Ayed et al. 27 .This inconsistency in the results could be due to the conditions of the experiment in terms of chick strain, the age of chickens, feed composition, or oil type and levels.Fatty acids, especially omega-3, have the potential to lessen oxidative stress, improve immune function, altered lipid synthesis, and reduce inflammation leading to improving gut health, and resulting in improving nutrient transport 28 , thus improving growth performance, this was confirmed by the current study.
One of the biggest losses that occur in the poultry industry is the deterioration in carcass traits during environmental heat stress.Our results indicated that exposure of broilers to environmental heat stress led to impairment of carcass traits in the control group.Our results indicated that adding different dietary oil sources to the diet improved carcass traits by increasing the dressing and reducing the content of abdominal fat.Similar results were obtained by Lu et al. 29 , who found an increase in carcass yield and a decrease in abdominal fat with the addition of oil to the diets.The lower abdominal fat content may be due to the role that the added oil plays in regulating the deposition of fat in the carcass.Some studies showed that the types of fatty acids affect the quality of the carcass through the ease of deposition and oxidation of unsaturated fatty acids 30 .In addition, the carcass weight is a proportional measurement of the live body weight of broilers, the increase in carcass meat was due to a proportional reduction of abdominal fat weight or improvement in BWG.The decrease in abdominal fat content can be explained by the role of dietary oils in promoting fatty acid β-oxidation (by decreasing the number of abdominal adipose cells) and inhibiting the absorption of dietary fat and fatty acid biosynthesis, and thus the abdominal fat percentage decreased significantly in the current study 30 .The decrease in abdominal fat resulting from adding oil to the diet is of great economic importance to the poultry industry, as abdominal fat is considered waste because it reduces carcass yield 31,32 .Furthermore, the distribution of fat between the different parts of the carcass tissues is of great importance to the quality, flavor, and freshness of the carcass and its nutritional value 33 .Our results confirm the effect of supplementing with oil on regulating the distribution of fat inside the carcass, which has a significant economic role in addition to enhancing meat quality.
Nutrient digestibility was studied to determine the extent to of chicken benefited from nutrients under the conditions of high temperatures.In the current study, the digestion of CF and CP was not affected, while the DM increased with the addition of oil compared to the control group.However, a slight increase in CF was observed in SO, CO, and OO groups compared to FO and CON groups.The effect of dietary oil on the digestion of nutrients varies based on the composition of the oil, the type, and the length of saturated or unsaturated fatty chains 34 .Nevertheless, the reason for the improvement in the digestion of DM can be attributed to the fact that the addition of oil led to a reduction in the rate of feed passage in the gut, which enhances the ability to digest and absorb nutrients 35 .Results of the current study indicated that there was no effect from different dietary oil sources on the activity of digestive enzymes.These results are similar to previous findings 36 .However, there was a numerical increase in amylase activity with the inclusion of OO and CO.In addition, the inclusion of OO, CO, and SO led to a numerical increase in lipase.A previous study indicated higher activities of some enzymes when supplementing with different oil sources 37 .In general, the digestive enzyme activities were consistent with www.nature.com/scientificreports/improved growth under hot conditions.It's known that heat stress leads to reduced feed intake, resulting in an imbalance in energy and small intestine functions (impairs nutrient absorption) through the change in the expression of the digestive enzymes (lipase, amylase, trypsin).During the heat stress period, amylase, lipase, and trypsin expression significantly decreased as a result of the impairment in intestinal function and structure 30,38 .Most importantly, heat stress reduces intestinal expression of the fatty acid-binding protein, which is involved in fatty acid uptake and transport 39 .In addition, a study found certain feed additives that target reducing oxidative stress and inflammation 28 , such as n-3 fatty acids, enhanced gut health in addition to enhancing nutrient absorption in the small intestine.In conclusion, the addition of dietary oils may have a role in changing gene expression, which may increase the digestive enzymes activity, thus enhancing nutrient digestion and absorption.The plasma biochemistry of birds varied by the different oil sources, and there were noticeable effects on liver enzymes and thyroid hormones.The composition of fatty acids in the diet had a significant effect on the features of plasma lipids, despite that, blood fats were not affected in our study which could be due to the oil burning for energy and dissipation of heat stress that the bird was exposed to 40 .This beneficial effect on the health of the broiler is indicated by the increase in the level of HDL in the plasma.Oil source has a noticeable effect on the concentration of AST and ALT as it decreased in the OO and CO groups.This result can be explained by the beneficial effect of PUFA on the safety of the liver by maintaining the integrity of the liver cell membrane and the fact that some oils contain antioxidants and antimicrobial effects that enhance liver functions 9,41 .Thyroid hormones were measured for their important role in the metabolism process 42 .Our results show a decrease in the level of thyroid hormones (T3 and T4) in the control group, which is in correspondence to Dahlke et al. 43 and Sohail et al. 44 , who noticed a decrease in T3 and T4 levels in birds exposed to high temperatures.Plasma levels of T3 and T4 increased as a result of feeding chickens an oil-supplemented diet in this experiment, which led to an improvement in broiler performance.
The oxidation status was evaluated to compare to what the previous studies showed of the harmful effect of oxidative stress during heat stress on the performance of the bird 45,46 .In the current study, the oxidation state improved significantly by including oils in the diet.This was confirmed by the increase in SOD and the decrease in MDA in plasma.In addition, there were clear, insignificant differences in the extent of improvement in the oxidation state depending on the oil source due to the biologically active compounds in each oil (such as tocopherols).Biological compounds play an important role in protecting the cell membrane from free radicals, which leads to enhancing chicken health 47 .The results of this study confirm the beneficial effect of adding oils to diets on enhancing the oxidative capacity of broilers exposed to environmental heat stress, which contributes to reducing oxidative degradation, resulting in strengthening immune functions and stability of poultry meat during heat stress.This is consistent with the results presented by Rymer et al. 48and Lindblom et al. 49 .
Consumers are becoming interested in the importance of keeping track of the health aspects associated with food.Since poultry is the main source of protein in developing countries because it contains a low content of fat, which is associated with the prevention of some diseases.As indicated by previous studies that the amount or composition of fatty acids in chicken tissues can be modified by manipulating the composition of dietary fatty acids 50 .Feeding broilers with different oils significantly affected the fatty acid profile of broiler chicken meat.Higher content of oleic acid (C18:1 ω9) was found in broilers fed on olive oil (OO).These results are consistent with the data of Zhang et al. 51 who indicated that the meat of broilers fed a diet supplemented with different levels of olive oil had the highest content of oleic acid (C18:1 ω9).Long et al. 52 demonstrated that the addition of fish oil to broiler diets significantly increased the oleic acid content in broiler breast meat.The highest content of linoleic acid and linolenic acid was found in the meat of the broiler fed on soybean oil (SO).These results are consistent with that obtained by Zaki et al. 53 , and Ayed et al. 27 who indicated that a higher content of linoleic acid and linolenic acid were found in the meat of broiler fed on rations containing soybean oil.The highest PUFA: SFA ratio was found in broilers fed on SO, while the lowest ratio was found in the FO feeding group.These results agree with Zaki et al. 53 who found that feeding broilers soybean oils had a higher PUFA: SFA ratio than other feeding groups.Furthermore, Long et al. 52 reported that the addition of fish oil to broiler diets significantly lowered the PUFA: SFA ratio.Types of oil significantly affected the ω6:ω3 ratio.The lowest ratio was found in the FO group.These results are close to that obtained by Panda et al. 54 who indicated that the incorporation of fish oil in broiler diets resulted in a significant decrease in the ω6:ω3 ratio.Moreover, Ibrahim et al. 55 found that supplementing broiler diets with fish oils reduced the ω6:ω3 ratio in broiler chicken meat.In the present study, the meat of broilers fed OO, CO, and SO had a higher ratio of UFA: SFA than those fed FO, and control, which indicates that the broiler's consumption of OO, CO, and SO posed a lower risk of diseases such as heart diseases.Our results confirmed that adding oil to a broiler diet modified breast muscle fatty acid profile.
In our results, different dietary oil sources had no significant effect on the pH values of meat.These results are consistent with the data of Ebeid et al. 56 and Pekel et al. 57 who found that different dietary oil sources had no significant effects on the pH value of meat.Data on cooking loss indicated that supplementing broiler diets with different types of oils had no significant effect on the cooking loss of chicken meat.These results are agreeing with Tavárez et al. 45 and Pekel et al. 57 who found that different sources of oils had no significant effect on cooking loss of breast chicken meat.Our data on chilling loss is consistent with Omojola et al. 58 who found that supplementing broiler diets with different oil sources had no significant effect on chilling loss.Nevertheless, our results indicated that feeding on different sources of oil significantly affected on shear force value of broiler meat.The results of the current study contradict the findings of Ebeid et al. 56 who found insignificant differences in the meat of chickens fed on different types of oils.Pekel et al. 57 indicated that feeding broilers on diets supplemented with different types of oils had no significant effect on the shear force of meat.Data of color measurements indicated that feeding broilers on different dietary oil types significantly affected on color characteristics of broiler chicken meat in our result.This result is similar to Ayed et al. 27 who found significant differences in color measurements of broiler chicken meat fed on diets supplemented with different oils.In contrast, Pekel et al. 57 found that feeding broilers on diets supplemented with different oils had no significant effect on meat color.
In our study, feeding broiler chickens with different sources of oils under heat stress conditions had a significant effect on TBA values on broiler meat.Attia et al. 26 reported that during hot weather conditions, the TBA value increased due to the peroxidation process, which is similar to our results.Supplementing broiler diets with oils significantly affected on oxidative stability of chickens exposed to heat stress 59 .Similar results were obtained by Abdulla 60 who indicated that feeding broiler chicken with different dietary oils significantly affected the TBA values of chicken meat.The same results were discovered by Ebeid et al. 56 who stated that feeding broilers with different types of oils significantly improved the antioxidant status of meat.In the current study, the results indicated that the lowest TBA values were in the OO and FO feeding groups.This result is similar to that obtained by Tufarelli et al 61 .who found that supplementing the broiler diet with olive oil significantly affected the TBA value of meat compared to the other dietary oils due to its high content of phenolic compounds which increases the oxidative stability in meat.Similarly, Ibrahim et al. 55 indicated that supplementing the broiler diet with fish oil significantly decreased the TBA value compared with different types of oils.It can be concluded that the addition of oil to broiler diets, especially olive oil, and fish oil, improved meat quality, which encourage consumers to purchase broiler meat.

Conclusion
Supplementing with dietary oils has proven to be effective in alleviating the detrimental effects of environmental heat stress in broilers.Adding different dietary oil sources led to an improvement in growth performance, and enhanced the oxidative status, and plasma lipid index, furthermore, it improved carcass characteristics, and meat quality in broilers exposed to environmental heat stress.Olive oil and soybean oil, respectively, had the best effect on performance and meat quality.However, we need further studies to reveal the effect of mixing dietary oil or using individual fatty acids as a means of reducing the harmful effects of heat stress on chicken performance.

Materials and methods
The Animal Care and Research Ethics Committee of Desert Research Center, Egypt, approved the animal care protocol used for this experiment.

Birds, diets, and experimental design
The experiment was conducted at the Siwa Research Station of the Desert Research Center.The experiment began in June 2021 (during summer), temperature and humidity were recorded twice daily (12 am and 12 pm), the average temperature was 31.7 ℃ and the relative humidity was 43% during the experimental period.The temperature was maintained the first day at 34 ℃, the second day at 33 ℃, the third and fourth days at 32 ℃, and starting from the fifth day the chicks were exposed to the ambient temperature until the end of the experiment.Six hundred twenty-five broiler chicks (Ross 308, unsexed) were purchased from a commercial hatchery in Cairo-Egypt, and distributed randomly to five groups, each having 5 replicates (25 chicks in each replicate).Chicks of the first group were fed a diet without adding oil, and the second to the fifth group were fed a diet containing 3% soybean oil, corn oil, olive oil, and fish oil, respectively.Chicks were fed at two phases: the first was the starter diet from the age of 1 to 21 days and the second was the grower diet from the age of 22-35 days (Tables 7, 8), the feed compositions were formulated based on the National Research Council 62 .Feed and water were offered ad libitum, and the lighting was continued throughout the trial period.

Nutrient digestibility
At the end of the trial period (35 days), six broilers per group were weighed and individually caged in metabolic pens and starved for 8 h to begin the digestion experiment, and their excreta were collected for three days (three times a day).The approximate analysis of the dry matter, crude fat, and crude protein of diets and dried excreta were estimated according to AOAC 63 .

Plasma biochemical analysis
Ten blood samples from each group (two samples from each replicate) at day 35 were collected from the brachial vein with a vacationer heparinized tube and separated by centrifugation at 2500×g for 15 min at 4 °C to determine the plasma biochemical constituents.Triglyceride, total cholesterol, low-density cholesterol (LDL), and high-density cholesterol (HDL) concentrations in the plasma were estimated.In addition, the activities of plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), superoxide dismutase (SOD), malondialdehyde (MDA), as well as the glutathione peroxidase (GPx) were determined by using commercial kits (Spinreact Co. Girona, Spain).Plasma thyroxine (T4) and triiodothyronine (T3) hormone concentrations were assayed by radioimmunoassay with a commercial kit, as evidence of thyroid status.

Digestive enzymes activity
Intestine content samples were collected from different regions (duodenum, jejunum, and ileum), and preserved in a neutral saline solution, then the mixture was centrifuged (1,792 g for 15min), and the supernatant was separated to estimate the concentrations of digestive enzymes.Lipase, amylase, and trypsin activity were determined using the method described by Sklan and Halevy 64 , Pinchasov et al. 65 , and Sklan et al. 66 , respectively.

Table 2 .
Effect of adding different dietary oil sources on carcass characteristics and nutrient digestibility of broilers under environmental heat stress.
a-cMeans within the same row with different superscripts differ.CON without additional oil, SO soy oil, CO corn oil, OO olive oil, FO fish oil, SEM standard error of means.

Table 3 .
Effect of adding different dietary oil sources on plasma lipid, liver enzymes, and thyroid hormones of broilers under environmental heat stress.a-c Means within the same row with different superscripts differ.CON without additional oil, SO soy oil, CO corn oil, OO olive oil, FO fish oil, T3 triiodothyronine, T4 thyroxine, CHO cholesterol, TRI triglyceride, HDL high-density cholesterol, LDL low-density cholesterol, ALT alanine aminotransferase, AST aspartate aminotransferase.

Table 4 .
Effect of adding different dietary oil sources on digestive enzymes activity and antioxidative enzymes of broilers under environmental heat stress.a-c Means within the same row with different superscripts differ.CON without additional oil, SO soy oil, CO corn oil, OO olive oil, FO fish oil, SOD superoxide dismutase, MDA malondialdehyde, GPx glutathione peroxidase.

Table 5 .
Effect of adding different dietary oil sources on fatty acids content in the breast of broilers under environmental heat stress.
a-cMeans within the same row with different superscripts differ.CON without additional oil, SO soy oil, CO corn oil, OO olive oil, FO fish oil, SFA saturated fatty acids, USFA unsaturated fatty acids, PUFA polyunsaturated fatty acids.
Vol.:(0123456789) Scientific Reports | (2023) 13:20179 | https://doi.org/10.1038/s41598-023-47356-6www.nature.com/scientificreports/Performance response Live body weight (LBW), feed intake (FI), and mortality count of each replicate were recorded daily, and the feed conversion ratio (FCR), and the European Production Efficiency Factor (EPEF) were calculated at days 21, and 35.At 35 days of age, six chicks from each treatment group were randomly taken to represent all treatment replicates to measure parameters.The feed was removed 12 h before slaughter and carcass characteristics were estimated.The weight of carcass (dressing), abdominal fat, liver, thigh muscle, and breast muscle were recorded and expressed as a ratio to live body weight.